Authorities in Binh Khe Commune, Gia Lai Province, said the crash occurred at about 10.55 pm on May 10 on the section of An Khe Pass running through the commune.
According to initial reports, a tipper lorry collided with the rear of the passenger coach while both vehicles were travelling in the same direction.
The impact caused the coach to lose control and plunge about 30 metres into a ravine.
There were 12 people on board at the time of the accident, including the driver and passengers.
A 38-year-old male passenger was killed in the crash. Two other passengers, aged 35 and 36, suffered serious injuries and were taken to Gia Lai Central General Hospital for treatment.
The remaining passengers sustained minor injuries and were transferred to Tay Son Medical Centre for medical checks and monitoring.
Emergency services arrived shortly after the incident to carry out rescue operations, remove victims from the wreckage and regulate traffic along the An Khe Pass route.
